1. Field of the Invention
The present invention relates to a low-transmission transparent layered structure comprising a transparent substrate and a low-transmission transparent layer formed thereon, or a transparent substrate and two layer films made of a low-transmission transparent layer and a transparent coat layer successively formed thereon, which is used as a front plate, etc., of a display device such as, for example, a cathode ray tube (CRT), etc. Particularly, the invention relates to a low-transmission transparent layered structure which has a flat transmission profile, can further impart a low reflectance and antistatic and electric field shielding functions, and can reduce the production cost thereof, and also a production method of the layered structure and also a display device to which the low-transmission transparent layered structure is applied.
2. Description of Related Art
With recent development of office automation, the chance of working close to the display of a cathode ray tube (CRT) of a computer has been increased, in this case, it is required of the display that the displayed image is easy to see and it does not give a visual tired feeling, and also in a home color television, and the easiness of seeing the displayed image. For satisfying these requirements, as the case may be, a treatment of improving the contrast by lowering the transmittance. of the front surface glass of CRT is carried out.
In this case, a method of using a face panel (the front face panel of CRT) having a low transmittance and a method of applying a coating having a low transmittance, to a face panel having a relatively high transmittance considered but from the point that the transmittance of CRT can be freely controlled, the latter method is advantageous.
Thus, there is considered a method of coating the face panel of CRT with a coating liquid formed by dispersing carbon fine particles, which are generally widely used as black pigment fine particles, in a solvent on the face panel of CRT, but by this method, there is a problem that the transmission profile of the film formed is lowered in the short wavelength side of a visible light as shown in Comparative Example 1 of FIG. 1 and the coated film becomes a brownish transmission color.
Also, as other attempt of making easy to see a displayed image, it has been carried out to applying an anti-glare treatment on the surface of a face panel to restrain the reflection of the image. For example, the anti-glare treatment may be practiced even by a method of forming fine roughness on the surface of the face panel to increase the diffused reflection at the surface, but because in the case of using this method, the resolution is lowered to deteriorate the image quality, the method cannot be said to be so preferred.
Accordingly, it is preferred to carry out the anti-glare treatment by an interference method of controlling the refractive index and the film thickness of the transparent film so that the reflected light rather causes a destructive interference to the incident light. To obtained the low reflection effect by such an interference method, a double layer structure film wherein the optical film thicknesses of the high refractive index film and the low refractive index film are established to 1/4xcex and 1/4xcex, 1/2xcex and 1/4xcex (xcex: wavelength) is generally employed.
Thus, there is a method of using carbon fine particles as the black pigment fine particles, after coating a coating liquid formed by dispersing the carbon fine particles in a solvent on the face panel of CRT followed by drying, over-coating thereon a coating liquid made of a silica sol, etc., as the main constituent, and heat-treating the coated layer at about 200xc2x0 C. to obtain a film of a low reflectance as the double layer structure film. By this method, good reflection characteristics as shown in Comparative Example 4 of FIG. 2 are obtained but there is the problem as described above that the transmission profile of the film is lowered in the short wavelength side of a visible light as shown in Comparative Example 4 of FIG. 7 to give a brownish transmittance color.
Now, in the case of working close to CRT, there is a case of being required that there is neither attaching of dust nor electric shock by the electrostatic charging on the surface of CRT in addition to that the displayed image is easy to see and does not give visually tired feeling. Furthermore, in addition to these requirements, recently, bad influences of the low-frequency electromagnetic waves generated from CRT to a human body are anxious about and it has also been desired to CRT that such an electromagnetic wave does not leak outside.
The electromagnetic waves are generated from deflecting coils and flyback transformers and the leakage of magnetic fields can be prevented in its greater part by designing, e.g., by the changing of deflecting coils in shape. As for the leakage of electric fields, it can be prevented by forming a transparent electrically conductive layer on the surface of the face panel of CRT.
Measures to prevent such leakage of electric fields are theoretically the same as: the countermeasures taken in recent years to prevent electrostatic charging. However, it has been desired that the surface resistance of the transparent electrically conductive layer is from about 108 to 1010 xcexa9/square for the electrostatic charging prevention and is at most 106 xcexa9/square for electric field shielding.
Thus, to cope with the various requirements described above, a method using tin antimony oxide (ATO) fine particles or indium tin oxide (ITO) fine conductive particles as the transparent fine conductive particles, and after coating a transparent conductive fine particle-containing coating liquid formed by dispersing the transparent conductive fine particles in a solvent together with a binder such as an alkyl silicate on the face panel of CRT followed by drying, heat-treating the coated layer at a temperature of about 200xc2x0 C. to form a transparent electrically conductive layer is known.
However, because the above-described transparent conductive fine particles used in the method do not absorb a visible light, to obtain a low-transmission film for improving the contrast, it is necessary to incorporate carbon fine particles, etc., in the transparent electrically conductive layer, and when carbon fine particles are incorporated, there is a problem that a flat transmission profile is not obtained and the film coated is colored in a brownish color as in the above-described case.
The present invention has been made in view of the problems described above and an object of this invention is to provide a low-transmission transparent layered structure having particularly a flat transmission profile, capable of imparting a low reflectance and an antistatic/electric field shielding function, and capable of reducing the production cost and also to a production method of the low-transmission transparent layered structure, and further to provide a display device to which the low-transmission transparent layered structure is applied.
The low-transmission transparent layered structure of the 1st embodiment of the invention for attaining the above-described objects is a low-transmission transparent layered structure comprising a transparent substrate and a low-transmission transparent layer formed on the transparent substrate, wherein the low-transmission transparent layer is constituted of black pigment fine particles having a mean particle size of from 10 to 150 nm and a binder matrix as the main constituents, the black pigment fine particles are composite oxide fine particles of iron, manganese, and copper, or they are carbon fine particles and black titanium compound fine particles, the transmission for visible light of the low-transmittance transparent layer is from 40 to 90%, and further the standard deviation of the transmission of the low-transmittance in each wavelength of every 5 nm of a visible light wavelength region (380 to 780 nm) is 5% or lower.
Also, in the low-transmission transparent layered structure of the 1st embodiment of this invention, the black titanium compound is black titanium oxide or black titanium oxynitride, the mixing ratio of the black titanium compound fine particles to the carbon fine particles is from 80 to 2500 parts by weight of the black titanium compound fine particles to 100 parts by weight of the carbon fine particles and the constituting ratio of the binder matrix to the black pigment fine particles in the low-transmission transparent layer is from 150 to 650 parts by weight of the binder matrix to 100 parts by weight of the black pigment fine particles.
Also, in the low-transmission transparent layered structure of the 1st embodiment of this invention, the low-transmission transparent layer further contains electrically conductive oxide fine particles having a mean particle size of from 10 to 150 nm, the compounding amount of the electrically conductive oxide fine particles is from 50 to 1000 parts by weight to 100 parts by weight of the black pigment fine particles, the surface resistance of low-transmission transparent layer is from 104 to 1010 xcexa9/square, the electrically conductive oxide fine particles are at least one kind of fine particles selected from indium tin oxide fine particles and tin antimony oxide fine particles, and further a double layer film formed by the low-transmission transparent layer and a transparent coat layer is formed on the transparent substrate. Also, in the low-transmission transparent layered structure described above, the reflectance of the low-transmission transparent layered structure, which becomes minimum in the reflection profile of a visible light region is 3or lower, the visible light transmittance of the double layer film is from 40 to 90%, and further the standard deviation of the transmittance of the double layer film in each wavelength of every 5 nm of a visible light wavelength region (380 to 780 nm) is 5% or lower.
Furthermore, the low-transmission transparent layered structure is a low-transmission transparent layered structure having a double layer film formed by forming the low-transmission transparent layer containing the electrically conductive oxide fine particles and a transparent coat layer on the transparent substrate, wherein the reflectance of the low-transmission transparent layered structure, which becomes minimum in the reflection profile of a visible light region, is 3% or lower, the surface resistance and the visible light transmittance of the double layer film are from 104 to 1010 xcexa9/square and from 40 to 90% respectively, and the standard deviation of the transmittance of the double layer film in each wavelength of every 5 nm of a visible light wavelength region (380 to 780 nm) is 5% or lower. Also, in the above-described low-transmission transparent layered structure, each of the binder matrix of the low-transmission transparent layer and the transparent coat layer are made of silicon oxide as the main constituent.
Then, in a method of producing a low-transmission transparent layered structure of the 2nd embodiment of this invention, a coating liquid formed by dispersing black pigment fine particles having a mean particle size of from 10 to 150 nm made of composite oxide fine particles of iron, manganese, and copper, or made of carbon fine particles and black titanium compound fine particles, and an inorganic binder constituting a binder matrix in a solvent as the main constituents is prepared and after coating the coating liquid on a transparent substrate, the layered structure thus coated is subjected to a heating treatment.
Also, in the method of producing a low-transmission transparent layered structure of the 2nd embodiment of this invention, the constituting ratio of the inorganic binder to the black pigment fine particles of the coating liquid is from 150 to 650 parts by weight of the inorganic binder to 100 parts by weight of the black pigment fine particles, the coating liquid further contains electrically conductive fine particles having a mean particle size of from 10 to 150 nm, and the compounding amount of the electrically conductive oxide fine particles is from 50 to 1000 parts by weight to 100 parts by weight of the black pigment fine particles.
In a method of producing a low-transmission transparent layered structure of the 3rd embodiment of this invention, a coating liquid formed by dispersing black pigment fine particles having a mean particle size of from 10 to 150 nm, made, of composite oxide fine particles of iron, manganese, and copper or made of carbon fine particles and black titanium compound fine particles in a solvent as the main constituent is prepared, the coating liquid is coated on a transparent substrate, and then after coating a coating liquid for forming a transparent coat layer, the layered structure coated is subjected to a heating treatment.
Also, in the method of producing a low-transmission transparent layered structure of the 3rd embodiment of this invention, the coating liquid further contains electrically conductive oxide fine particles having a mean particle size of from 10 to 150 nm, the compounding amount of the electrically conductive oxide fine particles is from 50 to 1000 parts by weight to 100 parts by weight of the above-described black pigment fine particles, the coating liquid further contains an inorganic binder constituting a binder matrix, and the electrically conductive oxide fine particles are at least one kind of fine particles selected from indium tin oxide fine particles and tin antimony oxide fine particles.
Moreover, in the method of producing a low-transmission transparent layered structure of the 2nd or 3rd embodiment of this invention, the black titanium compound is black titanium oxide or black titanium oxynitride, the mixing ratio of the black titanium compound fine particles to the carbon fine particles is from 80 to 2500 parts by. weight of the black titanium compound to 100 parts by weight of the carbon fine particles, and furthermore, the inorganic binder of each of the coating liquid for forming the transparent coat layer and the above-described coating liquid having dispersed therein the fine particles is made of a silica sol as the main constituent.
Then, a display device of the 4th embodiment of this invention is a display device comprising a main body and a front face plate disposed at the front face side of the main body, wherein the low-transmission transparent layered structure of the 1st embodiment is disposed with the low-transmission transparent layer side thereof outside as the front face plate.